1. Field of the Invention
The present invention relates to an apparatus of generating control signals for sequentially operating various devices incorporated in an electrophotographic copying machine in accordance with angular movement of a photosensitive drum rotatably supported therein.
2. Description of the Prior Art
In general, an electrophotographic copying machine is constructed, for example, as shown in FIG. 1. A photosensitive drum 1 is supported in the copying machine for rotation in an clockwise direction as seen in FIG. 1. Provided on an outer periphery of the drum 1 is a photosensitive layer which is uniformly charged by a corona discharge device 2 and is then exposed to a light image of an original 3 on a movable original carrier 4 by a light-image exposure device 5 thereby forming an electrostatic latent image corresponding to the light image on the photosensitive drum 1. The latent image is then changed into a toner image by a suitable developing device 6. On the other hand, a copy paper 7 is trimmed by a cutter 8 into a desired size and fed by feeding mechanisms 9 and 10 to be brought into contact with the photosensitive drum 1 bearing the toner image thereon. After the toner image has been transferred onto the copy paper 7 under the action of a transferring corona discharge device 11, the copy paper 7 is peeled off by a peeling pawl 12 from the photosensitive drum 1 and fed by a feeding mechanism 13 to a fixing device 14 by which the toner image is fused on the copy paper 7 to form a permanent copy image thereon. The copy paper 7 is then stacked on a tray 15 mounted on an outer frame of the copying machine. The toner remaining on the photosensitive drum 1 after the completion of the transfer of the toner image is removed by a cleaning device 16 to allow the photosensitive drum 1 for repeated use.
Since the electrophotographic copying machine has a number of processing devices as described above, it is a problem how to generate control signals for actuating those devices with preciseness and reliability.
As a prior art for generating such control signals in timed relationship with the angular movement of the photosensitive drum in the well-known electrophotographic copying machine, there is Japanese Laid-Open Patent Application No. 14345/1975 in which a plurality of cams is secured to a shaft of the photosensitive drum and micro-switches are provided in association with the cams for generating signals to control the starting of charging, the turning-on of an exposure lamp, the feeding of the copy paper, and so on. However, since this technical approach requires the plurality of cams and the corresponding number of micro-switches, there are many defects that a large space is occupied by the cams and the micro-switches in the copying machine, that precise adjustment and hence long time are required to mount the cams and the micro-switches in the copying machine in order to operate them in a desired manner, that the response time of the micro-switches varies, and that the contacts of the micro-switches may be oxidized by the influence of the corona discharge causing failure of their operation.